As the kids go back to school, your house may not be the only empty nest in the area. This summer’s drought conditions also had an impact on breeding wood ducks at Duck Creek Conservation Area.
If you’ve read our blog over the last couple years, you may recall that Dr. Peter Blums monitors the nest boxes at Duck Creek each year. His results for the 2012 breeding season are in. This year he recorded the lowest number of nesting attempts (60) and total eggs laid (853) for wood ducks since his research began in 1996. He accounts for these low numbers because of the dry habitat conditions.
Unlike other waterfowl species wood ducks can’t really “pack their lunch” and haul fat and protein reserves from their wintering grounds. Instead, once the females arrive in the spring they have to forage heavily on bugs, snails and crayfish to meet the requirements for egg production. Usually their dietary needs can be met within the flooded sloughs in the timber and emergent marsh. However, this spring we lacked the precipitation that typically recharges these habitats and makes the bugs easily available. Since there wasn’t adequate food, many of the potentially breeding wood ducks took a “rain check” this year at Duck Creek.
Despite the lower wood duck numbers, Peter did have some good news. The percentage of nest success was at an all-time high at 85%; typically percentage of successful nesting attempts is closer to 68%. Nesting efficiency was also a record high at 71%. This is the number of eggs laid divided by the number of ducklings that leave the nest box. Dump nesting is where other wood ducks or hooded mergansers lay their eggs in nests that are being incubated by another bird. If you are sitting on a pile of eggs (10-60 eggs potentially) not all of them will be incubated adequately and therefore will not hatch. This causes the average nest efficiency to be much lower, typically around 51%.
The hooded mergansers did not seem to be affected by the drought conditions. Over the last 17 years, there have always been fewer merganser nest attempts in the nest boxes, but the number has steadily increased over time. This trend continued in 2012. There were 23 hooded merganser nest attempts and 286 eggs laid in the monitored nest boxes. Although the nesting efficiency and nest success was higher than the long-term average, the difference was not as substantial as it was for wood ducks.
This year, only a handful of nests were depredated by black rat snakes or egg-pecking birds. Peter reported that the excessive heat did contribute to the death of developing embryos within two nests during the last week of June. However, on average in 2012, each successful nest attempt produced 8.6 ducklings. Last year’s average number of ducklings per nest was 11. When you look at the overall production, (605 wood ducks and 251 hooded merganser ducklings), the higher nest success and increase in the number hooded mergansers, the total production (856 ducklings) falls within the range that we’ve seen over the last 17 year (850-1000 ducklings).
Although, years with lower production are just part of the natural variability of habitat and population dynamics, severe conditions definitely get your attention. As with kids these days, even though you may have an empty nest this year, things could change and next year it could once again get a little crowded.
I’ve said it before and I’ll say it again, special thanks to Peter and his continued monitoring of our locally breeding wood ducks and hooded mergansers. It is always fascinating.